TOKYO (Reuters) - World number one Dinara Safina collapsed to a stunning 7-6 4-6 7-5 defeat by Taiwanese qualifier Chang Kai-chen at the Pan Pacific Open on Monday. The Russian, dumped out of the U.S. Open in the third round earlier this month, struggled from the start in her opening match against a player 131 places below her in the world rankings. "It's not an easy moment," Safina told reporters after surrendering her Tokyo title. "I had a lot of chances in the third set but I just let it go." "I didn't play the way I should. I never took her out of her comfort zone," added Safina, who had sat sobbing on the steps of the players' lounge after her latest setback. "I didn't do much to help myself." French Open champion Svetlana Kuznetsova followed her compatriot out of the tournament. The fifth seed was upset 7-5 4-6 6-3 by Germany's Andrea Petkovic, also a qualifier.Former Tokyo winner Maria Sharapova restored some pride for Russia, however, and gave the tournament sponsors some cheer with a battling 4-6 7-5 6-1 win over Italy's Francesca Schiavone. Safina's ownership of the number one spot has been a source of contention following her failure to win a maiden grand slam in 2009. A brief holiday from tennis after her New York flop did not look to have helped the Russian, who got off to a poor start in Tokyo by losing the first set tiebreak 7-5. THUMPING BACKHAND The Pan Pacific title holder, given a first-round bye at the $2 million tournament, rallied to take the second with a thumping backhand, pumping her fist and screeching "Come on"But after seizing an early break in the deciding set, Safina's nervousness resurfaced as she tamely surrendered her serve with a double-fault at 5-4 up. While Safina yelled at herself in Russian, the 18-year-old Chang kept her cool, completing the biggest win of her career by forcing Safina into wild forehand on her third match point. "I never came into the match thinking I was going to lose badly," said Chang after winning a marathon match in two hours and 44 minutes. "I just wanted to play tough." Former world number one Sharapova improved as her first-round match progressed, storming through the final set before closing out with a blistering forehand down the line. "I did a great job of hanging in there," said Sharapova, 25th in the world rankings following shoulder surgery last October. "I was a down a break in the second set. It was really important to stay patient. What I have learned is that it takes a really long time to come back and I'm okay with that. "I've been playing catch-up. I know that I've got to push myself more than I ever have in my career." Earlier, Ai Sugiyama's final WTA Tour appearance ended prematurely when the Japanese player retired from her first-round match with Russian Nadia Petrova while trailing 6-0 2-1.